Size fractionation of total Chl a larger and smaller than 8 μm data generated by Mike Mullin of the Marine Life Research Group, aboard CalCOFI (California Cooperative Oceanic Fisheries Investigations) cruises of the coast of California, January 1994 - October 1996.

Based on twelve quarterly cruises over three years, the relative importance and absolute biomass of phytoplankton retained on an 8 mu m-pore membrane filter increased as the depth of the nitricline decreased, even though biomass of macrozooplankton (potential grazers) also increased as the nitricline shoaled. The relative importance of greater than or equal to 8 mu m cells was inversely related to a proxy for their biomass-specific mortality (biomass of macrozooplankton/biomass of greater than or equal to 8 mu m cells), as was their "residual" biomass not predicted from the nitricline depth